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authorDavid Gibson <david@gibson.dropbear.id.au>2023-08-22 15:29:56 +1000
committerStefano Brivio <sbrivio@redhat.com>2023-08-22 12:15:30 +0200
commit5bf200ae8a1ab298cb393bf1956599d1178567cb (patch)
tree515a094e86cd613ba21963b59e1399ddc906286a /udp.h
parent8aa32009edb74aa1f0b6d58e759d5111a4713346 (diff)
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tcp, udp: Don't include destination address in partially precomputed csums
We partially prepopulate IP and TCP header structures including, amongst other things the destination address, which for IPv4 is always the known address of the guest/namespace. We partially precompute both the IPv4 header checksum and the TCP checksum based on this. In future we're going to want more flexibility with controlling the destination for IPv4 (as we already do for IPv6), so this precomputed value gets in the way. Therefore remove the IPv4 destination from the precomputed checksum and fold it into the checksum update when we actually send a packet. Doing this means we no longer need to recompute those partial sums when the destination address changes ({tcp,udp}_update_l2_buf()) and instead the computation can be moved to compile time. This means while we perform slightly more computations on each packet, we slightly reduce the amount of memory we need to access. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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